[2] [TASK] [Backend] [API] Implement GET /api/v1/telemetry/pings endpoint

[R4R35]

Description

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Add a GET endpoint to retrieve telemetry records filtered by storeId and itemId. Echipa 4 will rely on this endpoint to fetch raw pings for their clustering algorithms.

Scope

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• Add GET /api/v1/telemetry/pings?storeId=x&itemId=y in TelemetryController
• Add corresponding method in TelemetryService
• Add corresponding query in TelemetryRepository
• Return a list of TelemetryRecord as JSON

Done When

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• GET /api/v1/telemetry/pings?storeId=x&itemId=y returns matching records
• Returns empty list if no records match
• Returns 200 OK in both cases

Priority

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• 🟡 Medium